This invention relates generally to roll-up or upwardly-acting overhead doors. More particularly, the present invention relates to a roller assembly intended for use on a garage overhead door.
Upwardly-acting overhead doors are commonly utilized as garage doors and conventionally employ a plurality of door sections which are hinged together. Such overhead doors are generally supported on a pair of L-shaped tracks for permitting the door to move upwardly from a substantially vertical closed position to a substantially horizontal opened position. To permit this opening and closing movement, the garage door is provided with a plurality of roller support units disposed adjacent the side edges of the door. A roller of each roller support unit is rollingly engaged with and supported by the stationary L-shaped track. Commonly, the roller support unit also includes a pair of hinge halves which are fixed to the adjacent door sections and disposed in opposed relationship. The hinge halves support a metal hinge tube in which the shaft of the roller is received.
The roller of many conventional roller support units is composed of metal and the metal-to-metal contact between the roller and the L-shaped track produces a large amount of undesirable noise when the door moves one position to another. In addition, such roller support units are generally composed of ordinary steel to minimize the material cost. Although the roller support units are generally installed on the interior side of the overhead door, they receive significant exposure to the elements and are subject to rust and other corrosion problems. Such corrosion increases the amount of noise produced by the door and can lead to failure of the roller support unit.
In an attempt to improve upon the above-described roller support unit, some conventional roller support units are provided with plastic rollers which are rotatably mounted on a metal roller shaft. The amount of noise produced by such roller support units is lower than that produced by roller support units having metal rollers. In addition, the plastic rollers are not subject to corrosion. However, these roller support units are generally more expensive to manufacture than the all-steel roller units and therefore are not cost competitive.